Truncated leaflet for prosthetic heart valves

ABSTRACT

Described embodiments are directed toward prosthetic valves having leaflets of a particular shape that improves bending character without requiring a long length valve. In accordance with an embodiment, a prosthetic valve comprises a leaflet frame, a plurality of leaflets that are coupled to the leaflet frame, where each leaflet has a free edge and a base. The base of each leaflet is truncated in which the leaflet in cross section shows a line in an alpha plane onto the leaflet frame.

FIELD

The present disclosure relates generally to prosthetic valves and morespecifically synthetic flexible leaflet-type prosthetic valve devices,systems, and methods.

BACKGROUND

Bioprosthetic valves have been developed that attempt to mimic thefunction and performance of a native valve. Flexible leaflets arefabricated from biological tissue such as bovine pericardium. In somevalve designs the biological tissue is sewn onto a relatively rigidframe that supports the leaflets and provides dimensional stability whenimplanted. Although bioprosthetic valves can provide excellenthemodynamic and biomechanical performance in the short term, they areprone to calcification and cusp tears, among other failure modes,requiring reoperation and replacement.

Attempts have been made to use synthetic materials, such aspolyurethane, among others, as a substitute for the biological tissue,to provide a more durable flexible leaflet prosthetic valve, hereinreferred to as a synthetic leaflet valve (SLV). However, syntheticleaflet valves have not become a valid valve replacement option sincethey suffer premature failure, due to, among other things, suboptimaldesign and lack of a durable synthetic material.

The leaflet moves under the influence of fluid pressure. In operation,the leaflets open when the upstream fluid pressure exceeds thedownstream fluid pressure and close when the downstream fluid pressureexceeds the upstream fluid pressure. The free edges of the leafletscoapt under the influence of downstream fluid pressure closing the valveto prevent downstream blood from flowing retrograde through the valve.

A preferred shape of synthetic heart valve leaflets has been describedmany times, but each is different from the others. The variousthree-dimensional shapes range from spherical or cylindrical totruncated conical intersections with spheres and an “alpharabola”.

SUMMARY

Described embodiments are directed to an apparatus, system, and methodsfor valve replacement, such as cardiac valve replacement. Morespecifically, described embodiments are directed toward flexible leafletvalve devices in which a truncated segment at the base of the leaflet ispresent at or adjacent to the intersection with the frame.

In accordance with an embodiment, a prosthetic valve comprises a leafletframe, a plurality of leaflets that are coupled to the leaflet frame,where each leaflet has a free edge and a base. The base of each leafletis truncated in which the leaflet in cross section shows a line in analpha plane onto the leaflet frame.

In accordance with an embodiment, a prosthetic valve comprises a framehaving a generally tubular shape with attached film. The frame defines aplurality of leaflet windows. The film defines at least one leafletextending from each of the leaflet windows. Each leaflet two leafletsides, a planar central zone, a leaflet base and a free edge oppositethe leaflet base. The two leaflet sides diverge from the leaflet base.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the present disclosure and are incorporated in andconstitute a part of this specification, illustrate embodimentsdescribed herein, and together with the description serve to explain theprinciples discussed in this disclosure.

FIG. 1A is a sketch of an aortic valve;

FIG. 1B is a cross-section of the aortic valve of FIG. 1A showing theangles associated with a leaflet heart valve;

FIG. 2A is a side view of a prosthetic valve in accordance with anembodiment; and

FIG. 2B is a perspective view of the embodiment of the valve of FIG. 2A;

FIG. 2C is an axial view of an embodiment of a prosthetic valve in anopen configuration;

FIG. 2D is an axial view of the embodiment of the prosthetic valve ofFIG. 2A in a closed configuration;

FIG. 3 is a representation of an embodiment of a leaflet frame unrolledto a flat orientation;

FIG. 4A is a side view of an embodiment of a transcatheter deliverysystem within anatomy;

FIG. 4B is a side view of an embodiment of a surgical valve withinanatomy;

FIG. 5 is a side view of the leaflet frame on an assembly mandrel, inaccordance with an embodiment;

FIG. 6A is a side view of the leaflet frame on a cutting mandrel, inaccordance with an embodiment; and

FIG. 6B is a perspective view of the leaflet frame on the assemblymandrel of FIG. 6A.

DETAILED DESCRIPTION

Persons skilled in the art will readily appreciate that various aspectsof the present disclosure can be realized by any number of methods andapparatus configured to perform the intended functions. Stateddifferently, other methods and apparatuses can be incorporated herein toperform the intended functions. It should also be noted that theaccompanying drawing figures referred to herein are not necessarilydrawn to scale, but may be exaggerated to illustrate various aspects ofthe present disclosure, and in that regard, the drawing figures shouldnot be construed as limiting.

Although the embodiments herein may be described in connection withvarious principles and beliefs, the described embodiments should not bebound by theory. For example, embodiments are described herein inconnection with prosthetic valves, more specifically cardiac prostheticvalves. However, embodiments within the scope of this disclosure can beapplied toward any valve or mechanism of similar structure and/orfunction. Furthermore, embodiments within the scope of this disclosurecan be applied in non-cardiac applications.

The term leaflet as used herein in the context of prosthetic valves is acomponent of a one-way valve wherein the leaflet is operable to movebetween an open and closed position under the influence of a pressuredifferential. In an open position, the leaflet allows blood to flowthrough the valve. In a closed position, the leaflet substantiallyblocks retrograde flow through the valve. In embodiments comprisingmultiple leaflets, each leaflet cooperates with at least one neighboringleaflet to block the retrograde flow of blood. The pressure differentialin the blood is caused, for example, by the contraction of a ventricleor atrium of the heart, such pressure differential typically resultingfrom a fluid pressure building up on one side of the leaflets whenclosed. As the pressure on an inflow side of the valve rises above thepressure on the outflow side of the valve, the leaflets opens and bloodflows therethrough. As blood flows through the valve into a neighboringchamber or blood vessel, the pressure on the inflow side equalizes withthe pressure on the outflow side. As the pressure on the outflow side ofthe valve raises above the blood pressure on the inflow side of thevalve, the leaflet returns to the closed position generally preventingretrograde flow of blood through the valve.

The term membrane as used herein refers to a sheet of materialcomprising a single composition, such as, but not limited to, expandedfluoropolymer.

The term composite material as used herein refers to a combination of amembrane, such as, but not limited to, expanded fluoropolymer, and anelastomer, such as, but not limited to, a fluoroelastomer. The elastomermay be imbibed within a porous structure of the membrane, coated on oneor both sides of the membrane, or a combination of coated on and imbibedwithin the membrane.

The term laminate as used herein refers to multiple layers of membrane,composite material, or other materials, such as elastomer, andcombinations thereof.

The term film as used herein generically refers to one or more of themembrane, composite material, or laminate.

The term biocompatible material as used herein generically refers to afilm or a biological material, such as, but not limited to, bovinepericardium.

The term leaflet window is defined as that space that a frame definesfrom which a leaflet extends. The leaflet may extend from frame elementsor adjacent to frame elements and spaced apart therefrom.

The terms native valve orifice and tissue orifice refer to an anatomicalstructure into which a prosthetic valve may be placed. Such anatomicalstructure includes, but is not limited to, a location wherein a cardiacvalve may or may not have been surgically removed. It is understood thatother anatomical structures that may receive a prosthetic valve include,but are not limited to, veins, arteries, ducts and shunts. Althoughreference is made herein to replacing a native valve with a prostheticvalve, it is understood and appreciated that a valve orifice or implantsite may also refer to a location in a synthetic or biological conduitthat may receive a valve for a particular purpose, and therefore thescope of the embodiments provided herein is not limited to valvereplacement.

As used herein, “couple” means to join, connect, attach, adhere, affix,or bond, whether directly or indirectly, and whether permanently ortemporarily.

As used herein, truncated or truncation refers to the sectioning of athree-dimensional body with a plane reducing the size of the body.Referring to FIG. 2D, a truncation zone is that area that may betruncated by the alpha plane so as to define an attachment line 145,i.e., a line of attachment, of the leaflet base 143.

Embodiments herein include various apparatus, systems, and methods for aprosthetic valve suitable for surgical and transcatheter placement, suchas, but not limited to, cardiac valve replacement. The valve is operableas a one-way valve wherein the valve defines a valve orifice into whichleaflets open to permit flow and close so as to occlude the valveorifice and prevent flow in response to differential fluid pressure.

The length of a leaflet heart valve is dictated by the angle the leafletmakes with respect to the enclosing frame. A longer leaflet has ashallower angle with respect to the frame. A shorter leaflet has asteeper angle with respect to the frame. A longer leaflet leads tobetter performance than a shorter leaflet. For most applicationshowever, only a short valve can fit into the recipient location. Thusthe valve designer is presented with a dilemma. In the instantembodiments, leaflet designs are provided that provide for goodperformance with a short leaflet, thus allowing short heart valves.

Valve

FIG. 1A is a sketch of an aortic valve 5. The leaflets 1 are coupled tothe aortic root 2 at the leaflet base 3. FIG. 1B is a cross-section ofthe aortic valve 5 of FIG. 1A showing the angles associated with aleaflet 1 of the aortic valve 5. FIG. 1B illustrates the relationshipbetween the leaflets 1 and a first horizontal line L1 extending throughthe leaflet base 3 at an attachment point 7, and a second horizontalline L2 extending through the tops 4 of the commissure. In FIG. 1B, theaortic valve 5 is oriented in a position with a valve axis X beingvertical, the inflow edge 6 is pointed downward, with the leaflets 1 inthe closed position. The attachment angle alpha (α) is defined as theangle between the tangent line Lt extending from the center of theleaflet base 3 of the leaflet 1 at the attachment point 7 and the firsthorizontal line L1 extending through the leaflet base 3 at theattachment point 7, as shown in FIG. 1.

It is understood that leaflets 1 may exhibit a concave, straight, orconvex shape in an axial cross-section through the center of the leafletbase 3 of the leaflet 1 at the attachment point 7. For the sake ofclarity and simplification of description of the embodiments presentedherein and not limited thereto, the geometry of a leaflet 1 is describedas having, in an axial cross-section through the center of the leafletbase 3 of the leaflet 1 at the attachment point 7, the tangent line Ltthat defines a as a straight line.

FIG. 2A is a side view of a prosthetic valve 100, in accordance with anembodiment. FIG. 2B is a perspective view of the prosthetic valve 100 ofFIG. 2A. FIGS. 2C and 2D are axial views of the prosthetic valve 100 ofFIG. 2A in an open and closed configuration, respectively. FIG. 3 is aside view of a leaflet frame 130 of the prosthetic valve 100 of FIG. 2Awherein the leaflet frame 130 has been longitudinally cut and laid opento better illustrate the elements of the generally tubular-shapedprosthetic valve 100. In FIGS. 2A and 2B, the leaflets 140 are shownslightly open as they are when held by the cutting mandrel 712. It isunderstood that a fully closed prosthetic valve 100 will have theleaflet free edges 142 of the leaflets 140, including the triple point148, coming together to coapt under the influence of downstream fluidpressure which results in closing the valve to prevent downstream bloodfrom flowing retrograde through the valve

Embodiments provided herein provide a solution to the tension betweendesiring a small alpha angle to have a short valve and a larger alphaangle resulting in longer leaflets for better leaflet bending behavior.Embodiments provided herein provide a larger alpha angle while reducingvalve length, by providing a leaflet that wherein the leaflet base 3 istruncated, providing a relatively flat leaflet base 143.

In accordance with embodiments herein, the attachment angle alpha (α) ofa given valve configuration is preserved as the leaflet height isreduced. This is accomplished by redefining the base of the leaflet notas an attachment point 7 as for the generally parabolic leaflet shape asshown in FIG. 1A, but as an attachment line 145 as shown in FIGS. 2A and2D, that is parallel to the horizontal line in the valve cross sectionalplane perpendicular to the valve axis X at the leaflet base 143 of theleaflet 140.

As a way to visualize embodiments provided herein, referring to FIG. 1B,the first horizontal line L1 extends through the leaflet base 3 as itmoves perpendicular along the valve axis X towards the commissure tops4. A plane containing the first horizontal line L1 and perpendicular tothe valve axis X, referred to as the alpha plane AP, intersects theleaflet 140 of FIG. 2A along a line of attachment 145. The leaflet base3 is truncated by the alpha plane AP, where the attachment point 7 ofthe leaflet base 3 becomes an attachment line 145, that is, a line ofattachment rather than a point, of the leaflet base 143 as shown in FIG.2A, 2B and 2D, as compared with leaflet base 3 of the leaflet 1 at theattachment point 7 shown in FIG. 1A.

Referring to FIG. 2D, an apex line La is indicated connecting the apices147 of the leaflets 140. The apex line La divides the leaflet 140 into afirst region 149 a adjacent the leaflet frame 130, and a second region149 b adjacent the leaflet free edge 142. The first region 149 a definesa truncated zone. The truncated zone is located on the lower section ofthe leaflet 140 adjacent the leaflet base 143. The truncation zone isthat area that may be truncated by the alpha plane AP so as to define anattachment line 145, that is, a line of attachment, of the leaflet base143.

Frame

Referring to FIGS. 2A-2D, the leaflet frame 130 is a generally tubularmember defining a generally open pattern of apertures 122, in accordancewith an embodiment. In accordance with transcatheter embodiments, theleaflet frame 130 is operable to allow it 120 to be compressed andexpanded between different diameters. The leaflet frame 130 comprises aframe first end 121 a and a frame second end 121 b opposite the framefirst end 121 a. The leaflet frame 130 comprises a leaflet frame outersurface 126 a and a leaflet frame inner surface 126 b opposite theleaflet frame outer surface 126 a, as shown in FIG. 2A. The leafletframe 130 defines commissure posts 136 that couple to the leaflet freeedges 142.

The leaflet frame 130 may comprise a structure known in the art as astent. A stent is a tubular member that may have a small diametersuitable for percutaneous transcatheter delivery into the anatomy, andmay be expanded to a larger diameter when deployed into the anatomy.Stents having various designs and material properties are well known inthe art.

The leaflet frame 130 can define any number of features, repeatable orotherwise, such as geometric shapes and/or linear or meandering seriesof sinusoids. Geometric shapes can comprise any shape that facilitatessubstantially uniform circumferential compression and expansion. Theleaflet frame 130 may comprise a cut tube, or any other element suitablefor the particular purpose. The leaflet frame 130 may be etched, cut,laser cut, or stamped into a tube or a sheet of material, with the sheetthen formed into a substantially cylindrical structure. Alternatively,an elongated material, such as a wire, bendable strip, or a seriesthereof, can be bent or braided and formed into a substantiallycylindrical structure wherein the walls of the cylinder comprise an openframework that is compressible to a smaller diameter in a generallyuniform and circumferential manner and expandable to a larger diameter.

The leaflet frame 130 can comprise any metallic or polymericbiocompatible material. For example, the leaflet frame 130 can comprisea material, such as, but not limited to nitinol, cobalt-nickel alloy,stainless steel, or polypropylene, acetyl homopolymer, acetyl copolymer,ePTFE, other alloys or polymers, or any other biocompatible materialhaving adequate physical and mechanical properties to function asdescribed herein.

In accordance with embodiments, the leaflet frame 130 can be configuredto provide positive engagement with an implant site to firmly anchor theprosthetic valve 100 to the site, as shown in FIG. 4A representing atranscatheter deployment of the prosthetic valve 100. In accordance withan embodiment, the leaflet frame 130 can comprise a sufficiently rigidframe having small elastic recoil so as to maintain sufficientapposition against a tissue orifice 150 to maintain position. Inaccordance with another embodiment, the leaflet frame 130 can beconfigured to expand to a diameter that is larger than a tissue orifice150 so that when prosthetic valve 100 expands into the tissue orifice150, it can be firmly seated therein. In accordance with anotherembodiment, the leaflet frame 130 can comprise one or more anchors (notshown) configured to engage the implant site, such as a tissue orifice150, to secure the prosthetic valve 100 to the implant site.

It is appreciated that other elements or means for coupling theprosthetic valve 100 to an implant site are anticipated. By way ofexample, but not limited thereto, other means, such as mechanical andadhesive means may be used to couple the prosthetic valve 100 to asynthetic or biological conduit.

As will be discussed later, the surgical prosthetic valve 100 embodimentmay or may not have the zigzag configuration since the surgicalprosthetic valve 100 may be of a fixed diameter and need not be operableto compress and re-expand.

FIG. 3 is a side view of the leaflet frame 130 wherein the leaflet frame130 has been longitudinally cut and laid open to better illustrate theelements of the leaflet frame 130 of the prosthetic valve 100 of FIG.2B. The leaflet frame 130 comprises a base element 138 and a pluralityof spaced apart isosceles triangle elements 174 interconnected by thebase element 138. Each leaflet window 137 is defined by a leaflet windowside 133 which is a side 175 of one triangle element 174 and anotherleaflet window side 133 which is a side 175 of an adjacent triangleelement 174, and wherein each leaflet window base 134 is defined by thebase element 138, wherein each leaflet window 137 defines an isoscelestrapezoid. In accordance with an embodiment of the prosthetic valve 100,each leaflet 140 has substantially the shape of an isosceles trapezoidhaving two leaflet sides 141, a leaflet base 143 and a leaflet free edge142 opposite the leaflet base 143, wherein the two leaflet sides 141diverge from the leaflet base 143, wherein the leaflet base 143 issubstantially flat, as shown in dashed lines in FIG. 3. The leafletframe 130 further defines commissure posts 136 from which the leafletfree edge 142 extends.

In accordance with an embodiment, the leaflet frame 130 comprises aframe first end and a frame second end opposite the frame first end, theleaflet window having a shape determined, at least in part, by wrappinga two dimensional isosceles trapezoid onto the tubular shape of theframe, the isosceles trapezoid having a base and two sides that divergefrom the base, and wherein a side from adjacent isosceles trapezoidsmeet at the frame second end.

In transcatheter prosthetic valve 100 embodiments, the leaflet frame 130is elastically, plastically, or both, compressible to obtain arelatively small diameter to accommodate percutaneous transcathetermounting and delivery

In accordance with an embodiment, the leaflet frame 130 comprise a shapememory material operable to flex under load and retain its originalshape when the load is removed, thus allowing the leaflet frame 130 toself-expand from a compressed shape to a predetermined shape. Inaccordance with an embodiment the leaflet frame 130 is plasticallydeformable to be expanded by a balloon. In another embodiment theleaflet frame 130 is elastically deformable so as to be self-expanding.

Film

The film 160 is generally any sheet-like material that is biologicallycompatible and configured to couple to leaflets to the frame, inaccordance with embodiments. It is understood that the term “film” isused generically for one or more biocompatible materials suitable for aparticular purpose. The leaflets 140 are also comprised of the film 160.

In accordance with an embodiment, the biocompatible material is a film160 that is not of a biological source and that is sufficiently flexibleand strong for the particular purpose, such as a biocompatible polymer.In an embodiment, the film 160 comprises a biocompatible polymer that iscombined with an elastomer, referred to as a composite.

Details of various types of film 160 are discussed below. In anembodiment, the film 160 may be formed from a generally tubular materialto at least partially cover the leaflet frame 130. The film 160 cancomprise one or more of a membrane, composite material, or laminate.Details of various types of film 160 are discussed below.

Leaflet

Each leaflet window 137 is provided with a biocompatible material, suchas a film 160, which is coupled to a portion of the leaflet window sides133 with the film 160 defining a leaflet 140, as shown in FIG. 2A and 3.Each leaflet 140 defines a leaflet free edge 142 and a leaflet base 143,in accordance with an embodiment. As will be described below, it isanticipated that a plurality of embodiments of leaflet base 143configurations may be provided. In accordance with an embodiment, thefilm 160 is coupled to a portion of the leaflet window sides 133 and tothe leaflet window base 134 where the leaflet 140 is defined by theportion of the leaflet window sides 133 and to the leaflet window base134. In accordance with another embodiment, the film 160 is coupled to aportion of the leaflet window sides

When the leaflets 140 are in a fully open position, the prosthetic valve100 presents a substantially circular valve orifice 102 as shown in FIG.2C. Fluid flow is permitted through the valve orifice 102 when theleaflets 140 are in an open position.

As the leaflets 140 cycle between the open and closed positions, theleaflets 140 generally flex about the leaflet base 143 and the portionof the leaflet window sides 133 to which the leaflet are coupled. Whenthe prosthetic valve 100 is closed, generally about half of each leafletfree edge 142 abuts an adjacent half of a leaflet free edge 142 of anadjacent leaflet 140, as shown in FIG. 2D. The three leaflets 140 of theembodiment of FIG. 2D meet at a triple point 148. The valve orifice 102is occluded when the leaflets 140 are in the closed position stoppingfluid flow.

Referring to FIG. 2D, in accordance with an embodiment, each leaflet 140includes a central region 182 and two side regions 184 on opposite sidesof the central region 182. The central region 182 is defined by a shapesubstantially that of a triangle defined by two central region sides183, the leaflet base 143 and the leaflet free edge 142. The two centralregion sides 183 converge from the leaflet base 143 to the leaflet freeedge 142.

In accordance with an embodiment, the central region 182 issubstantially planar when the prosthetic valve 100 is in the closedposition.

The leaflet 140 can be configured to actuate at a pressure differentialin the blood caused, for example, by the contraction of a ventricle oratrium of the heart, such pressure differential typically resulting froma fluid pressure building up on one side of the prosthetic valve 100when closed. As the pressure on an inflow side of the prosthetic valve100 rises above the pressure on the outflow side of the prosthetic valve100, the leaflet 140 opens and blood flows therethrough. As blood flowsthrough the prosthetic valve 100 into a neighboring chamber or bloodvessel, the pressure equalizes. As the pressure on the outflow side ofthe prosthetic valve 100 rises above the blood pressure on the inflowside of the prosthetic valve 100, the leaflet 140 returns to the closedposition generally preventing the retrograde flow of blood through theinflow side of the prosthetic valve 100.

It is understood that the leaflet frame 130 may comprise any number ofleaflet windows 137, and thus leaflets 140, suitable for a particularpurpose, in accordance with embodiments. Leaflet frames 130 comprisingone, two, three or more leaflet windows 137 and corresponding leaflets140 are anticipated.

In accordance with an embodiment of a prosthetic valve 100 suitable fortranscatheter placement, the prosthetic valve 100 may be compressed intoa collapsed configuration having a smaller diameter and expanded into anexpanded configuration so that the prosthetic valve 100 can be deliveredvia catheter in the collapsed configuration and expanded upon deploymentwithin the tissue orifice 150 as shown in FIG. 4A. The leaflet frame 130can be operable to recover circumferential uniformity when transitioningfrom the collapsed configuration to the expanded configuration.

The prosthetic valve 100 may be mounted onto a delivery catheter,suitable for a particular purpose. The diameter of the prosthetic valve100 in the collapsed configuration is determined in part by thethickness of the frame and the leaflet thickness.

Leaflet Film

The biocompatible material that makes up the leaflet 140 can compriseany biological tissue or synthetic, biocompatible materials sufficientlycompliant and flexible, such as a biocompatible polymer. In anembodiment, the leaflet 140 comprises a biocompatible polymer that iscombined with an elastomer, referred to as a composite. A materialaccording to one embodiment includes a composite material comprising anexpanded fluoropolymer membrane, which comprises a plurality of spaceswithin a matrix of fibrils, and an elastomeric material. It should beappreciated that multiple types of fluoropolymer membranes and multipletypes of elastomeric materials can be combined to form a laminate whileremaining within the scope of the present disclosure. It should also beappreciated that the elastomeric material can include multipleelastomers, multiple types of non-elastomeric components, such asinorganic fillers, therapeutic agents, radiopaque markers, and the likewhile remaining within the scope of the present disclosure.

In accordance with an embodiment, the composite material includes anexpanded fluoropolymer material made from porous ePTFE membrane, forinstance as generally described in U.S. Pat. No. 7,306,729 to Bacino.

The expandable fluoropolymer, used to form the expanded fluoropolymermaterial described, may comprise PTFE homopolymer. In alternativeembodiments, blends of PTFE, expandable modified PTFE and/or expandedcopolymers of PTFE may be used. Non-limiting examples of suitablefluoropolymer materials are described in, for example, U.S. Pat. No.5,708,044, to Branca, U.S. Pat. No. 6,541,589, to Baillie, U.S. Pat. No.7,531,611, to Sabol et al., U.S. patent application Ser. No. 11/906,877,to Ford, and U.S. patent application Ser. No. 12/410,050, to Xu et al.

The expanded fluoropolymer membrane can comprise any suitablemicrostructure for achieving the desired leaflet performance. Inaccordance with an embodiment, the expanded fluoropolymer comprises amicrostructure of nodes interconnected by fibrils, such as described inU.S. Pat. No. 3,953,566 to Gore. The fibrils radially extend from thenodes in a plurality of directions, and the membrane has a generallyhomogeneous structure. Membranes having this microstructure maytypically exhibit a ratio of matrix tensile strength in two orthogonaldirections of less than 2, and possibly less than 1.5.

In another embodiment, the expanded fluoropolymer membrane has amicrostructure of substantially only fibrils, as is generally taught byU.S. Pat. No. 7,306,729, to Bacino. The expanded fluoropolymer membranehaving substantially only fibrils, can possess a high surface area, suchas greater than 20 m²/g, or greater than 25 m²/g, and in someembodiments can provide a highly balanced strength material having aproduct of matrix tensile strengths in two orthogonal directions of atleast 1.5×10⁵ MPa², and/or a ratio of matrix tensile strengths in twoorthogonal directions of less than 4, and possibly less than 1.5.

The expanded fluoropolymer membrane can be tailored to have any suitablethickness and mass to achieve the desired leaflet performance. By way ofexample, but not limited thereto, the leaflet 140 comprises an expandedfluoropolymer membrane having a thickness of about 0.1 μm. The expandedfluoropolymer membrane can possess a mass per area of about 1.15 g/m².Membranes according to an embodiment of the invention can have matrixtensile strengths of about 411 MPa in the longitudinal direction and 315MPa in the transverse direction.

Additional materials may be incorporated into the pores or within thematerial of the membranes or in between layers of membranes to enhancedesired properties of the leaflet. Composite materials described hereincan be tailored to have any suitable thickness and mass to achieve thedesired leaflet performance. Composite materials according toembodiments can include fluoropolymer membranes and have a thickness ofabout 1.9 μm and a mass per area of about 4.1 g/m².

The expanded fluoropolymer membrane combined with elastomer to form acomposite material provides the elements of the present disclosure withthe performance attributes required for use in high-cycle flexuralimplant applications, such as heart valve leaflets, in various ways. Forexample, the addition of the elastomer can improve the fatigueperformance of the leaflet by eliminating or reducing the stiffeningobserved with ePTFE-only materials. In addition, it may reduce thelikelihood that the material will undergo permanent set deformation,such as wrinkling or creasing, that could result in compromisedperformance. In one embodiment, the elastomer occupies substantially allof the pore volume or space within the porous structure of the expandedfluoropolymer membrane. In another embodiment the elastomer is presentin substantially all of the pores of the at least one fluoropolymerlayer. Having elastomer filling the pore volume or present insubstantially all of the pores reduces the space in which foreignmaterials can be undesirably incorporated into the composite. An exampleof such foreign material is calcium that may be drawn into the membranefrom contact with the blood. If calcium becomes incorporated into thecomposite material, as used in a heart valve leaflet, for example,mechanical damage can occur during cycling open and closed, thus leadingto the formation of holes in the leaflet and degradation inhemodynamics.

In an embodiment, the elastomer that is combined with the ePTFE is athermoplastic copolymer of tetrafluoroethylene (TFE) and perfluoromethylvinyl ether (PMVE), such as described in U.S. Pat. No. 7,462,675 toChang et al. As discussed above, the elastomer is combined with theexpanded fluoropolymer membrane such that the elastomer occupiessubstantially all of the void space or pores within the expandedfluoropolymer membrane to form a composite material. This filling of thepores of the expanded fluoropolymer membrane with elastomer can beperformed by a variety of methods. In one embodiment, a method offilling the pores of the expanded fluoropolymer membrane includes thesteps of dissolving the elastomer in a solvent suitable to create asolution with a viscosity and surface tension that is appropriate topartially or fully flow into the pores of the expanded fluoropolymermembrane and allow the solvent to evaporate, leaving the filler behind.

In one embodiment, the composite material comprises three layers: twoouter layers of ePTFE and an inner layer of a fluoroelastomer disposedtherebetween. Additional fluoroelastomers can be suitable and aredescribed in U.S. Publication No. 2004/0024448 to Chang et al.

In another embodiment, a method of filling the pores of the expandedfluoropolymer membrane includes the steps of delivering the filler via adispersion to partially or fully fill the pores of the expandedfluoropolymer membrane.

In another embodiment, a method of filling the pores of the expandedfluoropolymer membrane includes the steps of bringing the porousexpanded fluoropolymer membrane into contact with a sheet of theelastomer under conditions of heat and/or pressure that allow elastomerto flow into the pores of the expanded fluoropolymer membrane.

In another embodiment, a method of filling the pores of the expandedfluoropolymer membrane includes the steps of polymerizing the elastomerwithin the pores of the expanded fluoropolymer membrane by first fillingthe pores with a prepolymer of the elastomer and then at least partiallycuring the elastomer.

After reaching a minimum percent by weight of elastomer, the leafletsconstructed from fluoropolymer materials or ePTFE generally performedbetter with increasing percentages of elastomer resulting insignificantly increased cycle lives. In one embodiment, the elastomercombined with the ePTFE is a thermoplastic copolymer oftetrafluoroethylene and perfluoromethyl vinyl ether, such as describedin U.S. Pat. No. 7,462,675 to Chang et al., and other references thatwould be known to those of skill in the art. Other biocompatiblepolymers which can be suitable for use in leaflet 140 include but arenot limited to the groups of urethanes, silicones(organopolysiloxanes),copolymers of silicon-urethane, styrene/isobutylene copolymers,polyisobutylene, polyethylene-co-poly(vinyl acetate), polyestercopolymers, nylon copolymers, fluorinated hydrocarbon polymers andcopolymers or mixtures of each of the foregoing.

Other Considerations

In accordance with an embodiment, the prosthetic valve 100 can beconfigured to prevent interference with a heart conduction system by notcovering a bundle branch in the left ventricle when implanted, such asmight be encountered with an aortic valve replacement procedure. Forexample, the prosthetic valve 100 can comprise a length of less thanabout 25 mm or less than about 18 mm. The prosthetic valve 100 can alsocomprise an aspect ratio of less than one, wherein the ratio describesthe relationship between the length of the prosthetic valve 100 to theexpanded, functional diameter. However, the prosthetic valve 100 can beconstructed at any length and, more generally, any desirable dimension.

In a transcatheter embodiment, in a collapsed state, the prostheticvalve 100 can have a collapsed profile that is less than about 35% ofthe expanded profile. For example, the prosthetic valve 100 comprising a26 mm expanded diameter can have a collapsed diameter of less than about8 mm, or less than about 6 mm. The percent difference in diameter isdependent on dimensions and materials of the prosthetic valve 100 andits various applications, and therefore, the actual percent differenceis not limited by this disclosure.

The prosthetic valve 100 can further comprise a bio-active agent.Bio-active agents can be coated onto a portion or the entirety of thefilm 160 for controlled release of the agents once the prosthetic valve100 is implanted. The bio-active agents can include, but are not limitedto, vasodilator, anti-coagulants, anti-platelet, anti-thrombogenicagents such as, but not limited to, heparin. Other bio-active agents canalso include, but are not limited to agents such as, for example,anti-proliferative/antimitotic agents including natural products such asvinca alkaloids (i.e. vinblastine, vincristine, and vinorelbine),paclitaxel, epidipodophyllotoxins (i.e. etoposide, teniposide),antibiotics (dactinomycin (actinomycin D) daunorubicin, doxorubicin andidarubicin), anthracyclines, mitoxantrone, bleomycins, plicamycin(mithramycin) and mitomycin, enzymes (L-asparaginase which systemicallymetabolizes L-asparagine and deprives cells which do not have thecapacity to synthesize their own asparagine); antiplatelet agents suchas G(GP) IIb/IIIa inhibitors and vitronectin receptor antagonists;anti-proliferative/antimitotic alkylating agents such as nitrogenmustards (mechlorethamine, cyclophosphamide and analogs, melphalan,chlorambucil), ethylenimines and methylmelamines (hexamethylmelamine andthiotepa), alkyl sulfonates-busulfan, nitrosoureas (carmustine (BCNU)and analogs, streptozocin), trazenes-dacarbazinine (DTIC);anti-proliferative/antimitotic antimetabolites such as folic acidanalogs (methotrexate), pyrimidine analogs (fluorouracil, floxuridine,and cytarabine), purine analogs and related inhibitors (mercaptopurine,thioguanine, pentostatin and 2-chlorodeoxyadenosine {cladribine});platinum coordination complexes (cisplatin, carboplatin), procarbazine,hydroxyurea, mitotane, aminoglutethimide; hormones (i.e. estrogen);anti-coagulants (heparin, synthetic heparin salts and other inhibitorsof thrombin); fibrinolytic agents (such as tissue plasminogen activator,streptokinase and urokinase), aspirin, dipyridamole, ticlopidine,clopidogrel, abciximab; antimigratory; antisecretory (breveldin);anti-inflammatory: such as adrenocortical steroids (cortisol, cortisone,fludrocortisone, prednisone, prednisolone, 6α-methylprednisolone,triamcinolone, betamethasone, and dexamethasone), non-steroidal agents(salicylic acid derivatives i.e. aspirin; para-aminophenol derivativesi.e. acetominophen; indole and indene acetic acids (indomethacin,sulindac, and etodalac), heteroaryl acetic acids (tolmetin, diclofenac,and ketorolac), arylpropionic acids (ibuprofen and derivatives),anthranilic acids (mefenamic acid, and meclofenamic acid), enolic acids(piroxicam, tenoxicam, phenylbutazone, and oxyphenthatrazone),nabumetone, gold compounds (auranofin, aurothioglucose, gold sodiumthiomalate); immunosuppressives: (cyclosporine, tacrolimus (FK-506),sirolimus (rapamycin), azathioprine, mycophenolate mofetil); angiogenicagents: vascular endothelial growth factor (VEGF), fibroblast growthfactor (FGF); angiotensin receptor blockers; nitric oxide donors;anti-sense oligionucleotides and combinations thereof; cell cycleinhibitors, mTOR inhibitors, and growth factor receptor signaltransduction kinase inhibitors; retenoids; cyclin/CDK inhibitors; HMGco-enzyme reductase inhibitors (statins); and protease inhibitors.

Transcatheter Delivery System

In an embodiment, with reference to FIG. 4A, a valve delivery system 500comprises a prosthetic valve 100 having a collapsed configuration and anexpanded configuration as previously described and an elongated flexiblecatheter 480, such as a balloon catheter, configured to deploy theprosthetic valve 100 via catheter. The catheter 480 can comprise aballoon to expand the prosthetic valve 100 and/or if required, to touchup the prosthetic valve 100 to ensure proper seating. The prostheticvalve 100 can be mounted to the distal section of the catheter 480 fordelivery through the vasculature. In order to hold the valve in acollapsed configuration on the catheter 480, the valve delivery systemmay further comprise a removable sheath (not shown) to closely fit overthe transcatheter prosthetic valve 100.

A method of delivery can comprise the steps of radially compressing avalve into its collapsed configuration onto the distal end of anelongate flexible catheter having proximal and distal ends; deliveringthe valve to a tissue orifice, such as a native aortic valve orifice,via a transfemoral or transapical route, and expanding the valve intothe tissue orifice. The valve can be expanded by inflating a balloon.

A method of delivery can comprise the steps of radially compressing avalve into its collapsed configuration, onto the distal section of anelongated flexible catheter having proximal and distal ends. Arestraint, which can be connected to a tether that passes through theorifice of valve and the lumen of the catheter, is fitted around thecommissure posts 136 of the valve. The valve is then delivered to anative valve orifice, such as a native aortic valve orifice, via a routeof delivery and expanded into the native orifice. The route of deliverycan comprise a transfemoral or transapical route. The valve can beexpanded by inflating a balloon.

Surgical Embodiments

It is appreciated that the embodiments of the prosthetic valve 100 maybe surgically implanted rather than using transcatheter techniques.Embodiments of a surgically implanted prosthetic valve 100 may besubstantially the same as those described above, with the addition of asewing cuff 170 adjacent to the leaflet frame outer surface 126 a, shownin FIG. 4A, in accordance with an embodiment. The sewing cuff 170, whichis well known in the art, is operable to provide structure that receivessuture for coupling the prosthetic valve 100 to an implant site, such asthe tissue orifice 150. The sewing cuff 170 may comprise any suitablematerial, such as, but not limited to, double velour polyester. Thesewing cuff 170 may be located circumferentially around the leafletframe 130 or perivalvular depending from the leaflet frame 130.

Method of Making

Embodiments described herein also pertain to a method of making theprosthetic valve 100 embodiments as described herein. In order to makethe various embodiments, a cylindrical mandrel 710 can be used. Withreference to FIG. 5, the mandrel 710 comprises a structural formoperable to receive the leaflet frame 130 thereon.

Embodiments described herein also pertain to a method of making theprosthetic valve 100 embodiments as described herein. In order to makethe various embodiments, a cylindrical mandrel 710 can be used. Withreference to FIG. 5, the mandrel 710 comprises a structural formoperable to receive the leaflet frame 130 thereon. An embodiment of amethod of making a prosthetic valve 100 comprises the steps of wrappinga first layer of film 160, e.g., a composite as described herein, into atubular form about the mandrel 710; placing the leaflet frame 130 overthe first layer of film 160, as shown in FIG. 5; forming a second layerof film 160 over the leaflet frame 130; thermally setting the assembly;receiving the assembly over a cutting mandrel 712 as shown in FIGS. 6Aand 6B; cutting the film 160 across the leaflet window top within theleaflet window 137 resulting in the prosthetic valve 100 of FIGS. 2Aand. 2B. In FIGS. 2A and 2B, the leaflets 140 are shown slightly open asthey are when held by the cutting mandrel 712. It is understood that afully closed prosthetic valve 100 will have the leaflet free edges 142of the leaflets 140, including the triple point 148, coming together tocoapt under the influence of downstream fluid pressure which results inclosing the valve to prevent downstream blood from flowing retrogradethrough the valve.

EXAMPLE

In exemplary embodiments, a heart valve having polymeric leaflets formedfrom a composite material having an expanded fluoropolymer membrane andan elastomeric material and joined to a semi-rigid, non-collapsiblemetallic frame, and further a having strain relief was constructedaccording to the following process:

A valve frame was laser machined from a length of MP35N cobalt chromiumtube hard tempered with an outside diameter of 26.0 mm and a wallthickness of 0.6 mm in the shape. The frame was electro-polishedresulting in 0.0126 a mm material removal from each surface and leavingthe edges rounded. The frame was exposed to a surface roughening step toimprove adherence of leaflets to the frame. The frame was cleaned bysubmersion in an ultrasonic bath of acetone for approximately fiveminutes. The entire metal frame surface was then subjected to a plasmatreatment using equipment (e.g. PVA TePLa America, Inc Plasma Pen,Corona, Calif.) and methods commonly known to those having ordinaryskill in the art. This treatment also served to improve the wetting ofthe fluorinated ethylene propylene (FEP) adhesive.

FEP powder (Daikin America, Orangeburg N.Y.) was then applied to theframe. More specifically, the FEP powder was stirred to form an airborne“cloud” in an enclosed blending apparatus, such as a standard kitchentype blender, while the frame is suspended in the cloud. The frame wasexposed to the FEP powder cloud until a layer of powder was adhered tothe entire surface of the frame. The frame was then subjected to athermal treatment by placing it in a forced air oven set to 320° C. forapproximately three minutes. This caused the powder to melt and adhereas a thin coating over the entire frame. The frame was removed from theoven and left to cool to approximately room temperature.

A polymeric strain relief was attached to the frame in the followingmanner. A thin (122 μm) walled sintered 15 mm diameter ePTFE tube wasdisposed on a 24.5 mm vented metal mandrel by stretching radially over atapered mandrel. Two layers of a substantially nonporous ePTFE membranewith a continuous FEP coating was circumferentially wrapped on themandrel with the FEP side towards the mandrel. The wrapped mandrel wasplaced in a convection oven set to 320° C., heated for 20 minutes, andair cooled to room temperature. The ePTFE and substantially nonporousePTFE membrane combined to serve as an inner release liner and wasperforated using a scalpel blade to communicate pressure between thevent holes in the mandrel. This entire release liner is removed in alater step.

A 5 cm length of the thick (990μ) walled partially sintered 22 mm innerdiameter ePTFE tube (density=0.3 g/cm³) was disposed onto the 24.5 mmvented metal mandrel with release liner. The ePTFE tube inner diameterwas enlarged by stretching it on a tapered mandrel to accommodate thelarger mandrel diameter.

A thin (4 μm) film of type 1 FEP (ASTM D3368) was constructed using meltextrusion and stretching. One layer of the FEP was wrapped over the 5 cmlength of the ePTFE tube.

The FEP powder coated frame was disposed onto the vented metal mandrelgenerally in the middle of the 5 cm span of ePTFE tube and FEP film.

One layer of the FEP was wrapped over the frame and 5 cm length of theePTFE tube.

A second 5 cm length of the 990 μm thick/22 mm inner diameter ePTFE tubewas disposed onto the assembly layered onto 24.5 mm vented metal mandrelby stretching its radius over a tapered mandrel to accommodate thelarger construct diameter.

A substantially nonporous ePTFE membrane was configured into a cylinderat a diameter larger than the construct and placed over the assembly,referred to as sacrificial tube. Sintered ePTFE fiber (e.g. Gore®Rastex® Sewing Thread, Part #S024T2, Newark Del.) was used to seal bothends of the sacrificial tube against the mandrel.

The assembly, including the mandrel, was heated in a convection oven(temperature set point of 390° C.) capable of applying pneumaticpressure of 100 psi external to the sacrificial tube described abovewhile maintaining a vacuum internal to the mandrel. The assembly wascooked for 40 minutes such that the mandrel temperature reachedapproximately 360° C. (as measured by a thermocouple direct contact withthe inner diameter of the mandrel). The assembly was removed from theoven and allowed to cool to approximately room temperature while stillunder 100 psi pressure and vacuum.

The Rastex® fiber and sacrificial tube was then removed. Approximately30 psi of pressure was applied to the internal diameter of the mandrelto assist in removal of the assembly. The inner release liner was peeledaway from the internal diameter of the assembly by inverting the linerand axially pulling it apart.

Excess polymeric material was trimmed with a scalpel and removed fromthe leaflet windows and bottom of the frame leaving approximately 0.5 to1.0 mm of material overhang.

A leaflet material was then prepared. A membrane of ePTFE wasmanufactured according to the general teachings described in U.S. Pat.No. 7,306,729. The ePTFE membrane had a mass per area of 0.452 g/m², athickness of about 508 nm, a matrix tensile strength of 705 MPa in thelongitudinal direction and 385 MPa in the transverse direction. Thismembrane was imbibed with a fluoroelastomer. The copolymer consistsessentially of between about 65 and 70 weight percent perfluoromethylvinyl ether and complementally about 35 and 30 weight percenttetrafluoroethylene.

The fluoroelastomer was dissolved in Novec HFE7500 (3M, St Paul, Minn.)in a 2.5% concentration. The solution was coated using a mayer bar ontothe ePTFE membrane (while being supported by a polypropylene releasefilm) and dried in a convection oven set to 145° C. for 30 seconds.After 2 coating steps, the final ePTFE/fluoroelastomer or composite hada mass per area of 1.75 g/m², 29.3% fluoropolymer by weight, a domeburst strength of about 8.6 KPa, and thickness of 0.81 μm.

The frame encapsulated with polymeric material defining a strain reliefwas then attached to the leaflet material in a cylindrical or tubularshape in the following manner. A release liner was disposed on a 24.5 mmvented mandrel and perforated using a scalpel blade to communicatepressure between the vent holes in the mandrel.

The frame with polymeric strain relief was disposed onto the releaseliner covering the vented metal mandrel generally in the middle of the100 cm span of the mandrel.

Sixty-two layers of leaflet material were wrapped over the frame and 100cm length of the mandrel. Excess leaflet material was trimmed away witha scalpel from the mandrel adjacent to the vent holes.

A sacrificial tube was placed over the assembly and Rastex® fiber wasused to seal both ends of the sacrificial tube against the mandrel.

The assembly, including the mandrel, was heated in a convection oven(temperature set point of 390° C.) capable of applying pneumaticpressure of 100 psi external to the sacrificial tube described abovewhile maintaining a vacuum internal to the mandrel. The assembly wascooked for 23 minutes such that the mandrel temperature reachedapproximately 285° C. (as measured by a thermocouple direct contact withthe inner diameter of the mandrel). The assembly was removed from theoven and allowed to cool to approximately room temperature while stillunder 100 psi pressure and vacuum.

The Rastex® fiber and sacrificial tube were then removed. Approximately30 psi of pressure was applied inside the mandrel to assist in removalof the assembly. The inner release liner was peeled away from theinternal diameter of the assembly by inverting the liner and axiallypulling it apart.

The cylindrical shape of the frame and leaflet assembly was then moldedinto the final closed leaflet geometry in the following manner. Theassembly was placed onto a 24.5 mm vented mandrel with a cavity definingthe closed geometry of the leaflets.

Rastex® fiber was used to seal both ends of the leaflet tube against thecircumferential grooves in the mandrel.

The assembly, including the mandrel, was heated in a convection oven(temperature set point of 390° C.) capable of applying pneumaticpressure of 100 psi external to the sacrificial tube described abovewhile maintaining a vacuum internal to the mandrel. The assembly wascooked for 23 minutes such that the mandrel temperature reachedapproximately 285° C. (as measured by a thermocouple direct contact withthe inner diameter of the mandrel). The assembly was removed from theoven and allowed to cool to approximately room temperature while stillunder 100 psi pressure and vacuum. The Rastex® fiber was then removedand approximately 10 psi of pressure was applied to the internaldiameter of the mandrel to assist in removal of the assembly.

Excess leaflet material was trimmed generally along the free edge linedepicted in a cavity mold 714 of the cutting mandrel 712 shown in FIGS.6A and 6B.

The final leaflet was comprised of 28.22% fluoropolymer by weight with athickness of 50.3 μm. Each leaflet had 62 layers of the composite and aratio of thickness/number of layers of 0.81 μm.

The resulting prosthetic valve 100, as shown in FIGS. 2A-2D, includesleaflets 140 formed from a composite material with more than onefluoropolymer layer having a plurality of pores and an elastomer presentin substantially all of the pores of the more than one fluoropolymerlayer. Each leaflet 104 is movable between a closed position, shown inFIG. 2D, in which blood is substantially prevented from flowing throughthe valve assembly, and an open position, shown in FIG. 2C, in whichblood is allowed to flow through the valve assembly. Thus, the leaflets104 of the prosthetic valve 100 cycle between the closed and openpositions generally to regulate blood flow direction in a human patient.

The hydrodynamic performance was measured prior to accelerated weartesting. The performance values were: EOA=2.4 cm² and regurgitantfraction=11.94%.

The performance of the valve leaflets was characterized on a real-timepulse duplicator that measured typical anatomical pressures and flowsacross the valve. The flow performance was characterized by thefollowing process:

The valve assembly was potted into a silicone annular ring (supportstructure) to allow the valve assembly to be subsequently evaluated in areal-time pulse duplicator. The potting process was performed accordingto the recommendations of the pulse duplicator manufacturer (ViVitroLaboratories Inc., Victoria BC, Canada)

The potted valve assembly was then placed into a real-time left heartflow pulse duplicator system. The flow pulse duplicator system includedthe following components supplied by VSI Vivitro Systems Inc., VictoriaBC, Canada: a Super Pump, Servo Power Amplifier Part Number SPA 3891; aSuper Pump Head, Part Number SPH 5891B, 38.320 cm² cylinder area; avalve station/fixture; a Wave Form Generator, TriPack Part Number TP2001; a Sensor Interface, Part Number VB 2004; a Sensor AmplifierComponent, Part Number AM 9991; and a Square Wave Electro Magnetic FlowMeter, Carolina Medical Electronics Inc., East Bend, N.C., USA.

In general, the flow pulse duplicator system uses a fixed displacement,piston pump to produce a desired fluid flow through the valve undertest.

The heart flow pulse duplicator system was adjusted to produce thedesired flow (5 L/minutes), mean pressure (15 mmHg), and simulated pulserate (70 bpm). The valve under test was then cycled for about 5 to 20minutes.

Pressure and flow data were measured and collected during the testperiod, including right ventricular pressures, pulmonary pressures, flowrates, and pump piston position. Parameters used to characterize thevalve are effective orifice area and regurgitant fraction. The effectiveorifice area (EOA), which can be calculated as follows:EOA(cm²)=Q_(rms)/(51.6*(ΔP)^(1/2)) where Q_(rms) is the root mean squaresystolic/diastolic flow rate (cm³/s) and ΔP is the meansystolic/diastolic pressure drop (mmHg).

Another measure of the hydrodynamic performance of a valve is theregurgitant fraction, which is the amount of fluid or blood regurgitatedthrough the valve divided by the stroke volume.

As used in this application, the surface area per unit mass, expressedin units of m²/g, was measured using the Brunauer-Emmett-Teller (BET)method on a Coulter SA3100Gas Adsorption Analyzer, Beckman Coulter Inc.Fullerton Calif., USA. To perform the measurement, a sample was cut fromthe center of the expanded fluoropolymer membrane and placed into asmall sample tube. The mass of the sample was approximately 0.1 to 0.2g. The tube was placed into the Coulter SA-Prep Surface Area Outgasser(Model SA-Prep, P/n 5102014) from Beckman Coulter, Fullerton Calif., USAand purged at about 110° C. for about two hours with helium. The sampletube was then removed from the SA-Prep Outgasser and weighed. The sampletube was then placed into the SA3100 Gas adsorption Analyzer and the BETsurface area analysis was run in accordance with the instrumentinstructions using helium to calculate the free space and nitrogen asthe adsorbate gas.

Bubble point and mean flow pore size were measured according to thegeneral teachings of ASTM F31 6-03 using a capillary flow Porometer,Model CFP 1500AEXL from Porous Materials, Inc., Ithaca N.Y., USA. Thesample membrane was placed into the sample chamber and wet with SilWickSilicone Fluid (available from Porous Materials Inc.) having a surfacetension of about 20.1 dynes/cm. The bottom clamp of the sample chamberhad an about 2.54 cm diameter hole. Isopropyl alcohol was used as thetest fluid. Using the Capwin software version 7.73.012 the followingparameters were set as specified in the table below. As used herein,mean flow pore size and pore size are used interchangeably.

-   -   Parameter Set Point    -   Maxflow (cm³/m) 200000    -   Bublflow (cm³/m) 100    -   F/PT (old bubltime) 50    -   Minbpress (PSI) 0    -   Zerotime (sec) 1    -   V2incr (cts) 10    -   Preginc (cts) 1    -   Pulse delay(sec) 2    -   Maxpre (PSI) 500    -   Pulse width (sec) 0.2    -   Mineqtime (sec) 30    -   Presslew (cts) 10    -   Flowslew (cts) 50    -   Eqiter 3    -   Aveiter 20    -   Maxpdif (PSI) 0.1    -   Maxfdif (PSI) 50    -   Sartp (PSI) 1    -   Sartf (cm³/m) 500

Membrane thickness was measured by placing the membrane between the twoplates of a Kafer FZ1000/30 thickness snap gauge Kafer MessuhrenfabrikGmbH, Villingen-Schwenningen, Germany. The average of the threemeasurements was reported.

The presence of elastomer within the pores can be determined by severalmethods known to those having ordinary skill in the art, such as surfaceand/or cross section visual, or other analyses. These analyses can beperformed prior to and after the removal of elastomer from the leaflet.

Membrane samples were die cut to form rectangular sections about 2.54 cmby about 15.24 cm to measure the weight (using a Mettler-Toledoanalytical balance model AG204) and thickness (using a Kafer Fz1000/30snap gauge). Using these data, density was calculated with the followingformula: ρ=m/w*l*t, in which: ρ=density (g/cm³): m=mass (g), w=width(cm), l=length (cm), and t=thickness (cm. The average of threemeasurements was reported.

Tensile break load was measured using an INSTRON 122 tensile testmachine equipped with flat-faced grips and a 0.445 kN load cell. Thegauge length was about 5.08 cm and the cross-head speed was about 50.8cm/min. The sample dimensions were about 2.54 cm by about 15.24 cm. Forlongitudinal measurements, the longer dimension of the sample wasoriented in the highest strength direction. For the orthogonal MTSmeasurements, the larger dimension of the sample was orientedperpendicular to the highest strength direction. Each sample was weighedusing a Mettler Toledo Scale Model AG204, then the thickness measuredusing the Käfer FZ1000/30 snap gauge. The samples were then testedindividually on the tensile tester. Three different sections of eachsample were measured. The average of the three maximum loads (i.e., peakforce) measurements was reported. The longitudinal and transverse matrixtensile strengths (MTS) were calculated using the following equation:MTS=(maximum load/cross-section area)*(bulk density of PTFE)/(density ofthe porous membrane), wherein the bulk density of the PTFE was taken tobe about 2.2 g/cm³. Flexural stiffness was measured by following thegeneral procedures set forth in ASTM D790. Unless large test specimensare available, the test specimen must be scaled down. The testconditions were as follows. The leaflet specimens were measured on athree-point bending test apparatus employing sharp posts placedhorizontally about 5.08 mm from one another. An about 1.34 mm diametersteel bar weighing about 80 mg was used to cause deflection in the y(downward) direction, and the specimens were not restrained in the xdirection. The steel bar was slowly placed on the center point of themembrane specimen. After waiting about 5 minutes, the y deflection wasmeasured. Deflection of elastic beams supported as above can berepresented by: d=F*L³/48*EI, where F (in Newtons) is the load appliedat the center of the beam length, L (meters), so L=½ distance betweensuspending posts, and EI is the bending stiffness (Nm). From thisrelationship the value of EI can be calculated. For a rectangularcross-section: I=t³*w/12, where I=cross-sectional moment of inertia,t=specimen thickness (meters), w=specimen width (meters). With thisrelationship, the average modulus of elasticity over the measured rangeof bending deflection can be calculated.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present embodimentswithout departing from the spirit or scope of the embodiments. Thus, itis intended that the present embodiments cover the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

What is claimed:
 1. A prosthetic valve comprising: a leaflet frame; anda plurality of leaflets that are coupled to the leaflet frame, eachleaflet including a leaflet free edge and a leaflet base, wherein theleaflet base of each leaflet is truncated in which the leaflet in crosssection shows a line in an alpha plane onto the leaflet frame.
 2. Theprosthetic valve of claim 1, in which truncation of each leaflet islocated inferior and exterior to a line joining apices of two adjacentcommissural posts.
 3. The prosthetic valve of claim 1, in which thetruncation is a straight line across the leaflet base of the leaflet andperpendicular to a valve axis.
 4. The prosthetic valve of claim 1, theleaflet frame having a tubular shape, the leaflet frame defining aplurality of leaflet windows wherein each of the leaflet windowsincludes two leaflet window sides, a leaflet window base, and a leafletwindow top; and a film that is coupled to the leaflet frame and definingat least one of the plurality of leaflets extending from each of theleaflet windows, wherein each leaflet has a shape of an isoscelestrapezoid having two leaflet sides, a leaflet base and a leaflet freeedge opposite the leaflet base, wherein the two leaflet sides divergefrom the leaflet base, wherein the leaflet base is flat, wherein theleaflet base is coupled to the leaflet window base and wherein each ofthe two leaflet sides are coupled to one of the two leaflet windowsides.
 5. The prosthetic valve of claim 4, wherein each leaflet includesa central region and two side regions on opposite sides of the centralregion, wherein the central region is defined by a shape of an isoscelestriangle defined by two central region sides, the leaflet base and theleaflet free edge, wherein the two central region sides converge fromthe leaflet base, and wherein each of the two side regions have a shapeof a triangle where each of the two side regions are defined by one ofthe central region sides, one of the leaflet sides, and the leaflet freeedge.
 6. The prosthetic valve of claim 5, wherein the central region isplanar when the prosthetic valve is in a closed position underunpressurized conditions.
 7. The prosthetic valve of claim 5, whereinthe central region is planar when the prosthetic valve is in a closedposition.
 8. The prosthetic valve of claim 5, wherein the central regionis planar.
 9. The prosthetic valve of claim 4, wherein the leaflet framecomprises a leaflet frame first end and a leaflet frame second endopposite the leaflet frame first end, the leaflet window having a shapedetermined, at least in part, by wrapping a two dimensional isoscelestrapezoid onto the tubular shape of the leaflet frame, the isoscelestrapezoid having a base and two sides that diverge from the base, andwherein a side from adjacent isosceles trapezoids meet at the leafletframe second end.
 10. The prosthetic valve of claim 9, furthercomprising a commissure post extending axially from where the adjacentisosceles trapezoids meet, the commissure post having a length extendingto the leaflet frame second end.
 11. The prosthetic valve of claim 4,wherein the film is coupled to an outer surface of the leaflet frame.12. The prosthetic valve of claim 4, wherein the film is coupled to aninner surface of the leaflet frame.
 13. The prosthetic valve of claim 4,wherein the film is coupled to an inner surface and an outer surface ofthe leaflet frame.
 14. The prosthetic valve of claim 4, wherein theleaflet frame defines three interconnected leaflet windows having atriangular shape.
 15. The prosthetic valve of claim 4, wherein a leafletwindow side of one leaflet window is interconnected with a leafletwindow side of an adjacent leaflet window.
 16. The prosthetic valve ofclaim 4, wherein the prosthetic valve comprises a collapsedconfiguration and an expanded configuration for transcatheter delivery.17. The prosthetic valve of claim 4, wherein the leaflet comprises apolymeric material.
 18. The prosthetic valve of claim 17, wherein theleaflet comprises a laminate.
 19. The prosthetic valve of claim 18,wherein the laminate has more than one layer of a fluoropolymermembrane.
 20. The prosthetic valve of claim 4, wherein the film has atleast one layer of a fluoropolymer membrane having a plurality of poresand an elastomer present in the pores of the at least one layer offluoropolymer membrane.
 21. The prosthetic valve of claim 20, whereinthe film comprises less than about 80% fluoropolymer membrane by weight.22. The prosthetic valve of claim 20, wherein the elastomer comprises(per)fluoroalkylvinylethers (PAVE).
 23. The prosthetic valve of claim20, wherein the elastomer comprises a copolymer of tetrafluoroethyleneand perfluoromethyl vinyl ether.
 24. The prosthetic valve of claim 20,wherein the fluoropolymer membrane comprises ePTFE.
 25. The prostheticvalve of claim 1, further comprising: a film, wherein the leaflet framehas a tubular shape, the leaflet frame defining a plurality of leafletwindows wherein each of the leaflet windows includes two leaflet windowsides and a leaflet window base, wherein each leaflet window definesthree sides of an isosceles trapezoid, wherein the film is coupled tothe leaflet frame and defining at least one of the plurality of leafletsextending from each of the leaflet windows, wherein each leaflet has ashape of an isosceles trapezoid having two leaflet sides, a leaflet baseand a leaflet free edge opposite the leaflet base, wherein the twoleaflet sides diverge from the leaflet base, wherein the leaflet base isflat, wherein the leaflet base is coupled to the leaflet window base andwherein each of the two leaflet sides are coupled to one of the twoleaflet window sides.
 26. The prosthetic valve of claim 25, wherein eachleaflet includes a central region and two side regions on opposite sidesof the central region, wherein the central region is defined by a shapeof an isosceles triangle defined by two central region sides, theleaflet base and the leaflet free edge, wherein the two central regionsides converge from the leaflet base, and wherein each of the two sideregions have a shape of a triangle where each of the two side regionsare defined by one of the central region sides, one of the leafletsides, and the leaflet free edge.
 27. The prosthetic valve of claim 26,wherein the central region is planar when the prosthetic valve is in aclosed position under unpressurized conditions.
 28. The prosthetic valveof claim 26, wherein the central region is planar when the prostheticvalve is in a closed position.
 29. The prosthetic valve of claim 26,wherein the central region is planar.
 30. The prosthetic valve of claim25, wherein the leaflet comprises a polymeric material.
 31. Theprosthetic valve of claim 30, wherein the leaflet comprises a laminate.32. The prosthetic valve of claim 31, wherein the laminate has more thanone layer of a fluoropolymer membrane.
 33. The prosthetic valve of claim25, wherein the film has at least one layer of a fluoropolymer membranehaving a plurality of pores and an elastomer present in the pores of theat least one layer of fluoropolymer membrane.
 34. The prosthetic valveof claim 33, wherein the film comprises less than about 80%fluoropolymer membrane by weight.
 35. The prosthetic valve of claim 33,wherein the elastomer comprises (per)fluoroalkylvinylethers (PAVE). 36.The prosthetic valve of claim 33, wherein the elastomer comprises acopolymer of tetrafluoroethylene and perfluoromethyl vinyl ether. 37.The prosthetic valve of claim 33, wherein the fluoropolymer membranecomprises ePTFE.
 38. The prosthetic valve of claim 1, furthercomprising: a film, wherein the leaflet frame has a tubular shape, theleaflet frame defining a plurality of leaflet windows wherein each ofthe leaflet windows includes two leaflet window sides and a leafletwindow base, wherein, between each of the plurality of leaflet windows,the leaflet frame defines an isosceles triangle interconnected to eachother by a base element, the two leaflet window sides are defined by aside of one triangle and a side of an adjacent triangle, and whereineach leaflet window base is defined by the base element, wherein thefilm is coupled to the leaflet frame and defining at least one of theplurality of leaflets extending from each of the leaflet windows,wherein each leaflet has a shape of an isosceles trapezoid having twoleaflet sides, a leaflet base and a leaflet free edge opposite theleaflet base, wherein the two leaflet sides diverge from the leafletbase, wherein the leaflet base is flat, wherein the leaflet base iscoupled to the leaflet window base and wherein each of the two leafletsides are coupled to one of the two leaflet window sides.
 39. Theprosthetic valve of claim 38, wherein each leaflet includes a centralregion and two side regions on opposite sides of the central region,wherein the central region is defined by a shape of an isoscelestriangle defined by two central region sides, the leaflet base and theleaflet free edge, wherein the two central region sides converge fromthe leaflet base, and wherein each of the two side regions have a shapeof a triangle where each of the two side regions are defined by one ofthe central region sides, one of the leaflet sides, and the leaflet freeedge.
 40. The prosthetic valve of claim 39, wherein the central regionis planar when the prosthetic valve is in a closed position underunpressurized conditions.